Fixes #7922. Copy the donor event when simulating a bubbling submit in IE so that we don't accidentally stop propagation on it. Remove a bunch of return statements that could also cancel the event. DRY out the liveFired change from #6359 by moving it to the trigger() function.

Remove sed from post-build code, due to portability issues between GNU and BSD versions.
Follow up to ba43d37394b6018779d9a668c548e11579cd424a which apparently
didn't fix the problem completly on Mac OS X.

Enhances ajaxSetup so that it can take an optional target option, in which case target will be updated instead of ajaxSettings. That way, fields that shouldn't be deep extended can be listed and dealt with in one place. jQuery.ajax now makes use of ajaxSetup with target to create its internal settings object. Fixes #7531 in IE9RC.